Date: Thu, 10 Aug 2017 08:01:46 -0600 From: Alan Somers <asomers@freebsd.org> To: Ben RUBSON <ben.rubson@gmail.com> Cc: FreeBSD-scsi <freebsd-scsi@freebsd.org>, freebsd-hardware@freebsd.org Subject: Re: Do I need SAS drives?.. Message-ID: <CAOtMX2heJM1ekUowWdrri8x40JYFcYoQDrj0U45qSekO0C-ezQ@mail.gmail.com> In-Reply-To: <E50CE928-23D0-4415-A82C-FE2EA3D52512@gmail.com> References: <4DFBCE11-913A-4FC9-937D-463B4D49816C@aldan.algebra.com> <CAOtMX2jeUbSm535Zvd_7aHfQao-dMs5zbU0o3GRWk%2BcmW1Nq=g@mail.gmail.com> <E50CE928-23D0-4415-A82C-FE2EA3D52512@gmail.com>
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On Thu, Aug 10, 2017 at 7:44 AM, Ben RUBSON <ben.rubson@gmail.com> wrote: >> On 09 Aug 2017, at 17:59, Alan Somers <asomers@freebsd.org> wrote: >> >> 3) SAS drives have a lot of fancy features that you may not need or >> care about. For example, (...) their error >> reporting capabilities are more sophisticated than SMART > > Really interesting answer Alan, thank you very much ! > Slightly off-topic but I take this opportunity, > how do you check SAS drives health ? > I personally cron a background long test every 2 weeks (using smartmontools). > I did not experience SAS drive error yet, so not sure how this behaves. > Does the drive reports to FreeBSD when its read or write error rate cross > a threshold (so that we can replace it before it fails) ? > Or perhaps smartd will do ? > > As an example below a SAS error counter log returned by smartctl : > Errors Corrected by Total Correction Gigabytes Total > ECC rereads/ errors algorithm processed uncorrected > fast | delayed rewrites corrected invocations [10^9 bytes] errors > read: 0 49 0 49 233662 73743.588 0 > write: 0 3 0 3 83996 9118.895 0 > verify: 0 0 0 0 28712 0.000 0 > > Thank you ! > > Ben smartmontools is probably the best way to read SAS error logs. Interpreting them can be hard, though. The Backblaze blog is probably the best place to get current advice. But the easiest thing to do is certainly to wait until something fails hard. With ZFS, you can have up to 3 drives' worth of redundancy, and hotspares too. -Alan
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